As is known, RF antenna elements, such as radiating elements and feeding elements thereof, of antennas and antenna arrays can be encapsulated in an encapsulation material in order to be protected from external agents (such as atmospheric agents) that, otherwise, could alter characteristics of said RF antenna elements; for example, external agents, such as moisture or rain, can alter electromagnetic characteristics of, and/or oxidize, RF antenna elements.
In particular, encapsulation techniques based on thermosetting materials are currently known and used to manufacture antennas and antenna arrays. These encapsulation techniques normally exploit an injection molding process, which generally includes:                injecting a molten thermosetting material, such as a polyurethane-based foam, into a mold in which an RF antenna element, such as an RF printed circuit, has been previously inserted in order to be coated; and        causing the thermosetting material to solidify, whereby the thermosetting material solidifies into a protective conformal coating shaped by the mold and encapsulating the RF antenna element.        
Density and homogeneity of the thermosetting material are defined a priori on the basis of the electromagnetic characteristics of the RF antenna elements to be coated. In particular, density of the mixture injected into the mold normally is such that to enable repeatability of the process and represents, at the same time, a compromise between structural capabilities and electromagnetic performances of the encapsulated RF antenna elements.
An important parameter to be kept under control during an injection molding process is the injection pressure of the thermosetting resin into molds. In particular, this parameter can be kept under control by means of machines, such as foaming machine, which dose the materials, mixing and injecting them at a constant pressure into the molds. Many thermosetting materials commonly used for injection molding are obtained by mixing two compounds, that are injected into moulds and expand up to achieving a required density of the foam material. Foams based on polyurethane (PUR or PU) are broadly used to encapsulate RF antenna elements.
An example of use of a thermosetting material, in particular a PUR-based plastic material, to encapsulate RF antenna elements is provided in C. G. Pewsey, W. N. Klimczak, R. G. Farzin, “An Encapsulated Dipole Shaped Beam Array for Air Traffic Control”, Antennas and Propagation Society International Symposium, Chicago, July 1992, vol. 3, pp. 1418-1421. In particular, this paper concerns an encapsulated dipole array developed for use as an aircraft beacon interrogator antenna and designed to provide a highly-shaped beam. The encapsulation process described in this paper exploits a two-part reaction injection molding technique to encapsulate stripline, dipole and balun circuits in a ⅛-inch polyurethane plastic.
A further example of use of a thermosetting material to encapsulate RF printed circuits of an antenna array is provided in U.S. Pat. No. 5,285,212 (A), which relates to a self-supporting columnar antenna array including a printed circuit board that has, on one side thereof, a plurality of etched dipoles arranged in a linear array. On an opposite side of the circuit board is an excitation network for exciting each of the dipoles. The excitation network terminates in a connector to receive a radio frequency signal. The circuit board includes a plurality of openings in the spaces between the dipoles. An injection molding process encapsulates the circuit board in a thermosetting encapsulation material, namely Mobay 726 urethane. A supporting surface perpendicular to the printed circuit board extending through the openings is formed during the injection molding process. Integral mounting supports are formed in the encapsulation material at each end of the circuit board for facilitating mounting of the columnar array to a frame.
As is broadly known, thermosetting materials, such as PUR-based materials, can withstand extremely-high temperature, namely greater than 150° C., but tend after their life cycle:                not to be recyclable as a source for newly-made plastic; and        to entail a difficult and expensive disposal.        
Accordingly, RF antenna elements coated with thermosetting materials, such as PUR-based materials, suffer from the same disadvantages. In particular, this kind of RF antenna elements has a strong environmental impact, since, after the life cycle of these RF antenna elements, the thermosetting coating materials cannot be recycled and entail a difficult and expensive disposal.
Another aspect of thermosetting coating materials which should be carefully considered is related to painting. In fact, as is known, once an RF antenna element has been coated with a thermosetting coating material by means of an injection molding process, the resulting encapsulated RF antenna element is usually painted, not only for aesthetic reasons, but rather in order to protect it from ultraviolet (UV) rays. This painting process is generally known also as UV curing. The application of a painting for UV curing requires an accurate washing of the coated RF antenna element. In fact, specific chemicals are usually used in an injection molding process in order to facilitate, once the injection molding process has been accomplished, detachment of the coated RF antenna element from the mold. Unfortunately, these specific chemicals also prevents application of a painting for UV curing to the coated RF antenna element. Therefore, after detachment of the coated RF antenna element from the mold, an accurate washing of said coated RF antenna element is required in order to remove said specific chemicals and, thence, to enable the application of a painting for UV curing.